The invention relates to check valves in general, for example, to check valves of the type described in commonly owned U.S. Pat. No. 4,862,913 granted Sep. 5, 1989 to Dieter Wildfang for "Check Valve".
The patent to Wildfang discloses a check valve wherein a tubular housing confines an annular seat adjacent the inlet and a cage at the outlet. The cage serves to retain in the housing a reciprocable valving element which is biased against the seat by a spring but can yield to establish a path for the flow of fluid from the inlet toward and into the outlet when the pressure of fluid at the inlet suffices to overcome the bias of the spring. The spring reacts against the cage.
It is also known to employ a spherical valving element which is confined in the housing of a check valve and is movable toward and away from sealing engagement with a seat in the housing. The spherical valving element may but need not be biased toward the seat.
Presently known check valves are constructed and assembled in such a way that they can be put to specific uses, i.e., it is necessary to provide a selection of different check valves each of which can be used under a particular set of circumstances. For example, a first check valve can employ a spherical valving element which is capable of floating on a body of liquid in the housing of the check valve and is caused to sealingly engage the seat when the pressure at the outlet exceeds the pressure at the inlet of the housing. Another check valve can employ a relatively heavy spherical valving element which tends to sink and to thus move away from or against the seat. A further check valve can be designed in a manner as disclosed in the aforementioned patent to Wildfang, i.e., a coil spring can be used to bias a reciprocable nonspherical valve element toward its seat. The means for confining the valving element in the housing of a conventional check valve also vary from valve to valve, depending upon the shape and/or other characteristics of the valving element. All this contributes to the cost of the valves and to the cost of storing a variety of different check valves.